A nuclear reactor core has many, e.g., several hundred, individual fuel bundles that have different characteristics. Such bundles preferably are arranged within the reactor core so that the interaction between the fuel bundles satisfies all regulatory and reactor design constraints, including governmental and customer specified constraints. In addition to satisfying the design constraints, since the core loading arrangement determines the cycle energy, i.e., the amount of energy that the reactor core generates before the core needs to be refreshed with new fuel elements, the core loading arrangement preferably optimize the core cycle energy.
To optimize core cycle energy, the higher reactivity bundles generally are positioned at an inner core location. To satisfy some design constraints, however, higher reactivity bundles generally are positioned at an outer core location. Identifying the preferred core loading arrangement therefore is an optimization with constraints challenge.
The number of bundle arrangements, or configurations, possible in the reactor core can be in excess of one hundred factorial. Of these many different possible configurations, only a small percentage of such configurations satisfy all applicable design constraints. In addition, only a small percentage of the configurations that satisfy all applicable design constraints are economical.
Traditionally, core loading arrangement determinations are made on a trial and error basis. Specifically, and based on past experience of the engineers, a core loading arrangement is identified. The identified core loading arrangement is then simulated in a computer. If a particular design constraint is not satisfied by the identified arrangement, then the arrangement is modified and another computer simulation is run. Man-weeks of resources typically are required before an appropriate core loading arrangement is identified using the above described procedure.
In addition, once a core loading arrangement that satisfies all design constraints has been identified using the trial and error approach, such identified core arrangement may not provide the actual maximum cycle energy. Therefore, the trial and error process continues until the engineers believe that the optimum core arrangement has been identified. In practice, however, it is possible that a particular core arrangement that is not necessarily consistent with the engineers' past experience may be the actual optimum core arrangement. Such actual optimum core arrangement, however, may not necessarily be identified through the trial and error process.
Since the core arrangement problem generally is considered unique for each reactor and bundle characteristics, no known algorithm provides a viable solution for identifying optimum reactor core arrangements. In addition, expert systems have not been used on a broad basis since a standard set of rules typically are not applicable over a wide range of situations to the many unique and complex core loading arrangements which differ in all reactors.
It would be desirable, of course, to reduce the time required to identify a core loading arrangement which optimize cycle energy and satisfies all design constraints. It also would be desirable to provide a methodology applicable to a wide range of reactors for consistently and reliably identifying optimum core loading arrangements.